The present invention relates to an encoder method and apparatus for representing a digital image to provide a coded representation. The invention also relates to a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation.
The publication U.S. Pat. No. 5,754,793 discloses a wavelet based image compression scheme that utilises a human visual system (HVS model). The method adjusts quantisation both spectrally and spatially by having a quantisation factor based on edge state and background brightness for each coefficient in the DC subband, which is subsequently weighted by DWT level and orientation. The quantisation factors require no transmission overhead, but the method does require that there is no quantisation of the DC coefficients. It is in this way that the quantisation factors are able to be determined at both the encoder and the decoder. This limits the compression performance of the method and has the disadvantage of reducing the accuracy of the spatial adaption when the number of levels in the DWT increases, which is often required for high compression ratios. In addition, the method disclosed in the ""793 patent can not adapt to different viewing conditions or displays because the subband quantisation factors are stored in a look-up-table at the decoder. The method can also not be applied to a memory constrained coder because it requires coefficients from the DC subband to estimate the contrast masking in each subband.
It is an object of the present invention to ameliorate one or more disadvantages of the prior art.
According to one aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the steps of transforming the digital image to derive a plurality of blocks of coefficients, and embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients. The method further comprises the steps of determining a block rate for each encoded pass of each block, determining a distortion measure for each encoded pass of each block, terminating each encoded block at an encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of the block rates, and concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method includes the steps of transforming the digital image to derive a plurality of blocks of coefficients, and embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients. A block rate is determined for each encoded pass of each block, and a distortion measure is determined for each encoded pass of each block. Each encoded block is terminated at a encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion. The terminated encoded blocks are concatenated to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the step of transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The method further comprises the step of embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. A block rate is determined for each encoded pass of each bitplane of each block, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. A distortion measure is determined for each encoded pass of each bitplane of each block, wherein the distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. Each encoded block is terminated at an encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of block rates, and the terminated encoded blocks are concatenated to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the step of transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The method further comprises the step of embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. The method further comprises the step of determining a block rate for each encoded pass of each bitplane of each block, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. A distortion measure is determined for each encoded pass of each bitplane of each block, wherein the distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. Each encoded block is terminated at an encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion, and the terminated encoded blocks are concatenated to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The apparatus further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of the block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The apparatus further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The apparatus further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. First determination means is included for determining a block rate for each encoded pass of each bitplane of each block, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. Second determination means is included for determining a distortion measure for each encoded pass of each bitplane of each block, wherein the distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The apparatus further comprises means for terminating each encoded block at a an encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The apparatus further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. First determination means is included for determining a block rate for each encoded pass of each bitplane of each block, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. Second determination means is included for determining a distortion measure for each encoded pass of each bitplane of each block, wherein the distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The apparatus further comprises means for terminating each encoded block at an encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The computer program product further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The computer program product further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The computer program product further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. First determination means is included for determining a block rate for each encoded pass of each bitplane of each block, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. Second determination means is included for determining a distortion measure for each encoded pass of each bitplane of each block. The distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The computer program product further comprises means for terminating each encoded block at the encoded pass that minimizes image distortion based on the distortion measures for a predetermined total of block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The computer program product further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. First determination means is included for determining a block rate for each encoded pass of each bitplane of each block. The block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. Second determination means is included for determining a distortion measure for each encoded pass of each bitplane of each block. The distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The computer program product further comprises means for terminating each encoded block at an encoded pass that minimizes a total block rate based on the block rates for a predetermined image distortion, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the steps of transforming the digital image to derive a plurality of blocks of coefficients, embedded quadtree bitplane-coding, in one or more passes per bitplane, each block of coefficients, and determining a block rate for each encoded pass of each block. The method further comprises the steps of determining a distortion measure for each encoded pass of each block, terminating each encoded block at an encoded pass that minimizes a weighted sum of the image distortion based on the distortion values, and the total of the block rates, and concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the step of transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The method further comprises the step of embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. A block rate is determined for each encoded pass of each bitplane of each block. The block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective at least one part of the designated bitplane. A distortion measure is determined for each encoded pass of each bitplane of each block. The distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The method further comprises the steps of terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values, and concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a method of representing a digital image to provide a coded representation. The method comprises the steps of: (i) transforming the digital image to derive a plurality of blocks of coefficients; (ii) embedded bitplane encoding, in one or more passes per bitplane, each block of coefficients; (iii) determining a rate for each encoded pass of each block; (iv) determining a distortion measure for each encoded pass of each bitplane of each block, wherein the step of determining a distortion measure comprises the sub-steps of: (iv)(a) generating, for each original coefficient of each block, a weighted sum of magnitudes of neighboring coefficients; (iv)(b) calculating a threshold elevation, for each original coefficient of each block, based on the weighted sum; (iv)(c) calculating a distortion value for each encoded coefficient for each encoded pass of each block, wherein the distortion value for a designated encoded coefficient for a designated encoded pass of a designated block is based on the threshold elevation for the original coefficient corresponding to the designated encoded coefficient, and a value of the designated encoded coefficient as decoded from the encoded passes from the maximum bitplane corresponding to the designated block to respective at least one part of the designated bitplane; and (iv)(d) pooling the distortion values for each encoded coefficients to derive the distortion measure for each encoded pass of each bitplane of each block. The method further comprises the steps of (v) terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values; and (vi) concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane-encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The apparatus further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes a weighted sum of the image distortion based on the distortion values, and the total of the block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The apparatus further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. The apparatus further comprises means for determining a block rate for each encoded pass of each bitplane of each block. The block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective least one part of the designated bitplane. The apparatus further comprises means for determining a distortion measure for each encoded pass of each bitplane of each block. The distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The apparatus further comprises means for terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided an apparatus for representing a digital image to provide a coded representation. The apparatus comprises means for transforming the digital image to derive a plurality of blocks of coefficients, and means for embedded bitplane encoding, in one or more passes per bitplane, each block of coefficients. The apparatus further comprises first determination means for determining a rate for each encoded pass of each block, and second determination means for determining a distortion measure for each encoded pass of each bitplane of each block. The second determination means comprises means for generating, for each original coefficient of each block, a weighted sum of magnitudes of neighboring coefficients, and means for calculating a threshold elevation, for each original coefficient of each block, based on the weighted sum. The second determination means further comprises means for calculating a distortion value for each encoded coefficient for each encoded pass of each block, wherein the distortion value for a designated encoded coefficient for a designated encoded pass of a designated block is based on the threshold elevation for the original coefficient corresponding to the designated encoded coefficient, and a value of the designated encoded coefficient as decoded from the encoded passes from the maximum bitplane corresponding to the designated block to respective at least one part of the designated bitplane. The second determination means further comprises means for pooling the distortion values for each encoded coefficients to derive the distortion measure for each encoded pass of each bitplane of each block. The apparatus further comprises means for terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded quadtree bitplane-encoding, in one or more passes per bitplane, each block of coefficients, and means for determining a block rate for each encoded pass of each block. The apparatus further comprises means for determining a distortion measure for each encoded pass of each block, means for terminating each encoded block at an encoded pass that minimizes a weighted sum of the image distortion based on the distortion values, and the total of the block rates, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of original coefficients, wherein each block has a corresponding maximum bitplane and a corresponding minimum bitplane. The computer program product further comprises means for embedded quadtree bitplane encoding, in one or more passes per bitplane, each block of coefficients from the corresponding maximum bitplane to the corresponding minimum bit plane. Means for determining a block rate for each encoded pass of each bitplane of each block is included, wherein the block rate for a designated encoded pass of a designated bitplane of a designated block is representative of the number of code bits coded during the embedded quadtree bitplane encoding step of the designated block from its corresponding maximum bitplane to a respective least one part of the designated bitplane. Means for determining a distortion measure for each encoded pass of each bitplane of each block is included, wherein the distortion measure for a designated encoded pass of a designated bitplane of a designated block is a function of the coefficients decoded from the encoded passes from the maximum bitplane corresponding to the designated block to a respective at least one part of the designated bitplane and is a function of the original coefficients of the designated block. The apparatus further includes means for terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values, and means for concatenating the terminated encoded blocks to form the coded representation.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for representing a digital image to provide a coded representation. The computer program product comprises means for transforming the digital image to derive a plurality of blocks of coefficients, means for embedded bitplane encoding, in one or more passes per bitplane, each block of coefficients, and first determination means for determining a rate for each encoded pass of each block. The computer program product further comprises second determination means for determining a distortion measure for each encoded pass of each bitplane of each block. The second determination means comprises means for generating, for each original coefficient of each block, a weighted sum of magnitudes of neighboring coefficients, and means for calculating a threshold elevation, for each original coefficient of each block, based on the weighted sum. The second determination means further comprises means for calculating a distortion value for each encoded coefficient for each encoded pass of each block, wherein the distortion value for a designated encoded coefficient for a designated encoded pass of a designated block is based on the threshold elevation for the original coefficient corresponding to the designated encoded coefficient, and a value of the designated encoded coefficient as decoded from the encoded passes from the maximum bitplane corresponding to the designated block to respective at least one part of the designated bitplane. The second determination means further comprises means for pooling the distortion values for each encoded coefficients to derive the distortion measure for each encoded pass of each bitplane of each block. The computer program product further comprises means for terminating each encoded block at an encoded pass according to a function of the determined rates and distortion values, and means for concatenating the terminated encoded blocks to form the coded representation.